1. Field of the Invention
The present invention is directed to a process for rapid anaerobic digestion of biomass using microorganisms and the production of biofuels therefrom.
2. Description of the Background
In 2005, the United States consumed more than $715 billion in oil, with imported oil contributing to 35% of oil consumption, with that figure likely to rise to as much as 70% of consumption over the next 20 years. In an effort to alleviate this dependency, 1% of the U.S. corn crop was used to provide 1.7% of fuel demand as corn ethanol in 2004. Unfortunately, even if all corn grain now grown in the United States were converted to ethanol, only about 15% of current transportation needs would be satisfied. Thus, corn-derived ethanol cannot provide a significant alternative to imported oil as a source of fuel.
The U.S. government has set a goal of replacing 30% of the nation's gasoline consumption with ethanol by 2030, which has been estimated to require 60 billion gallons of ethanol per year and an annual supply of a billion metric tons of dry biomass. The U.S. Departments of Agriculture and Energy have both found it feasible to produce this amount of biomass provided that plant fiber in wood and grasses is included. Thus, an economical method of biomass conversion of plant fiber of wood and grass to fuel is required to meet the goal set by the U.S. government.
Most agricultural biomass is in the form of structural carbohydrates (cellulose and hemicellulose) bound to the polyphenolic polymer, lignin. One bottleneck for biomass conversion to biofuels and other utilizable products is the degradation of biomass to fermentable carbohydrates. A second bottleneck is the conversion of these carbohydrates to fuels like ethanol. Glucose, is fermented by yeast to ethanol, but five-carbon sugars, which make up about half of plant cell wall carbohydrate, are not rapidly metabolized to ethanol by known microorganisms. Fermentation products of cell wall degradation include volatile fatty acids, but these have not been shown to be converted to ethanol with existing technology.
Although industrial bioconversions have been conducted with pure microorganism cultures, such conventional bioconversions have not been used successfully in converting fibers in woods and grasses to ethanol.
Thus, a need exists for a means by which fibers in woods and grasses could be converted to biofuels, such as ethanol.